Present construction techniques in the housing construction industry involve building single and multiple-family homes with single-piece wood components like 2.times.4's, 2.times.6's and 2.times.10-inch fur and sheet stock, 4.times.8 foot in plywood and oriented-strandboard lumber. As opposed to pre-fabricated sections, all components are shipped to the homesite and assembled in a "stick-built" fashion using steel nails, screws and staples.
Crews who specialize in the specific phase of housing construction called "framing" do their work after the foundation is laid and before the house is roofed and sided. A typical 2500 square foot house can be framed in three days by a 5-person crew, working at a very fast pace. The typical activities done during the framing phase include working non-stop measuring and sawing wood, nailing wall sections, erecting the frames in place, and trimming at any time at several locations within the house. In addition to the fast work pace, the framing crews must use poor quality lumber and deal with nailing inaccuracies.
Field research reveals that about 90% of the sawing is done with a seven and one-quarter inch hand-held circular saw. The framer is not given the high-quality wood and wood materials that a cabinet or furniture-maker uses, nor is he or she concerned with doing the finished trim, where the cuts must be smooth and accurate. The framer has two major user-perceived needs. One, of course, is speed; the other is how long a given saw blade will last. The latter condition occurs when the framer notices that it takes more and more effort or bias to get the saw blade through the lumber. This is the signal for the framer to replace the blade (which is now perceived as no longer being "sharp") with a new one. To date, the old blades are not resharpened, because blades sold for this type of work are usually priced so low that it is not cost-effective for the construction company to resharpen the blades, or damage to the teeth is too severe.
It has been discovered that "edge wear" is neither the only, nor the primary condition that increases the likelihood that a given blade will feel like it has lost its "sharpness". Two significant factors with equal or greater impact on blade life is "tooth loss" and "breakage". These phenomena occur when the teeth encounter foreign matter in the wood, or a particularly stressful cutting application and the cutting edge is severely broken, or the tooth is removed completely. Therefore, the unchipped edges of the carbide teeth may remain sharp (have little edge wear), but the user nevertheless perceives that the saw blade has lost its "sharpness".
Unfortunately, the framer will probably have to use low-cost framing materials, which include dirty and gummy wood, and wood with loose nails and loose staples. When a carbide tooth, which is necessarily made of material much harder and more brittle than the steel of the saw blade itself, encounters these foreign materials, it is likely to chip or be torn off. However, it has been discovered that the very changes which one would consider to reduce chipping will also cause the tip to lose edge sharpness. Accordingly, the problem that the present invention addresses is this: how to minimize the likelihood that tooth damage will cause a given blade to require an unacceptable user bias force, while nevertheless maximizing the probability that the same blade will track the edge sharpness of a conventional carbide tipped blade.
If a blade can exhibit a significant drop in tooth damage, it will last longer in this most demanding of home construction environments.